Search PubMed⌕ Search

Biomedical subjects

S A Newman

Publications and source records attributed to S A Newman.

At least 19 recordsLinked to original sources
PubMed1992

Ciliary body adenoma in a 10-year-old girl who had a rhabdomyosarcoma.

A retrolenticular fibrovascular membrane occurred in the setting of a ciliary body mass in a 10-year-old black girl who had been successfully treated for a rhabdomyosarcoma of the lung. The results of a transscleral biopsy of the mass demonstrated it to be a pigmented adenoma of the ciliary body. A lensectomy and membranectomy were performed to aid in the follow-up and rehabilitation of the eye. At 9 months after surgery, the patient had 20/25 vision with no evidence of tumor growth. This case demonstrates an unusual cause of cyclitic membrane formation and suggests that transscleral biopsy may be a useful adjunct in the management of selected ciliary body masses.

Adenoma↗
PubMed1992

Neurological deterioration after lumbar cerebrospinal fluid drainage.

Large-bore lumbar spinal fluid drainage is used frequently as part of the preoperative and intraoperative management of patients undergoing cranial base tumor resection. Such drainage allows displacement of the brain with minimal force, thereby potentially decreasing retraction damage to it. We document 2 patients in whom serious complications resulted from lumbar drainage systems. These patients deteriorated into a coma state following cerebrospinal fluid (CSF) drainage. Reinfusion of synthetic CSF solutions caused a brisk return to normal neurological status. These plus other potential complications associated with lumbar drainage, such as persistent CSF leaks into the back and soft-tissue nerve root injury, warranted abandoning the lumbar cistern drainage route of CSF drainage in favor of drainage directly from the intracranial compartment. Depending on the particular operation performed, drainage of CSF near the cribriform plate, the suprachiasmatic cistern, or from the sylvian fissure may be effective sites for CSF drainage. Unlike lumbar drainage, intracranial CSF drainage does not have the added risk of promoting cerebral herniation.

Carcinoma, Squamous Cell↗
PubMed1992

Expression of developmentally defined retinal phenotypes in the histogenesis of retinoblastoma.

Retinoblastoma, the most common intraocular tumor of childhood, is a malignant neoplasm that arises during retinal development. The embryonal cell target for neoplastic transformation is not yet clearly defined. To better understand the histogenetic potential of this tumor, the expression of photoreceptor and glial cell-associated proteins were examined in 22 primary retinoblastomas. Interphotoreceptor retinol-binding protein (IRBP), cone and rod opsins were selected as the photoreceptor specific proteins due to their different temporal patterns of expression during normal retinal development. Neoplastic Müller cell differentiation, and non-neoplastic reactive astrocytes were identified using cellular retinaldehyde binding-protein (CRAlBP), and glial fibrillary acidic protein (GFAP), respectively. Photoreceptor proteins were present in 16 cases and showed different cellular patterns of expression. IRBP and cone opsin were usually abundant. Although rod opsin was clearly identified in eight tumors, its expression was more restricted than either IRBP or cone opsin. This differential pattern of expression, opposite to the normal pattern of photoreceptor gene expression in the adult retina, corresponded to a marked decrease in mRNA for rod opsin. Cone opsin and IRBP colocalized in fleurettes demonstrating that neoplastic human cone cells are capable of IRBP synthesis. Müller cell differentiation was present in 12 of the 16 cases in which photoreceptor proteins were detected. In contrast, GFAP was only present in reactive, stromal astrocytes associated with blood vessels. Our data suggest that the retinoblastoma has the histogenetic potential of the immature neural retinal epithelium which can give rise to both photoreceptor and Müller cell lineages. The differential expression of cone and rod phenotypes in retinoblastoma is consistent with the "default" mechanism of cone cell differentiation.

Blotting, Northern↗
PubMed1991

A rapid colorimetric assay for heparinase activity.

A rapid, sensitive, assay for enzymes that degrade heparin is described. The procedure is based on the interference of heparin with color development during the interaction of protein with the dye Coomassie brilliant blue. The loss of this property when the glycosaminoglycan is degraded by heparinase can be used to quantify activity of the enzyme in pure form, or in complex biological samples such as tissue homogenates or serum. The assay is also suitable for studying dependence of heparinase activity under conditions such as varying pH and temperature.

Colorimetry↗
PubMed1991

Interaction of fibronectin with heparin in model extracellular matrices: role of arginine residues and sulfate groups.

The interaction of heparin with the NH2-terminal domain of human plasma fibronectin was studied by using matrix-driven translocation, an assay for the adhesion of extracellular macromolecules with cell or particle surfaces within artificial collagen matrices. Partial desulfation of heparin rendered it ineffective in competitively inhibiting the interaction of the fibronectin NH2-terminal domain with heparin-coated particles, suggesting a role for sulfate groups of heparin in the interaction. Analysis of the fibronectin domain in terms of its primary structure, its proposed organization into "type I modules", and its hydrophilic and flexible segments led to the identification of several arginine-containing sites of potential interaction with the sulfate groups of heparin. Modification of increasing numbers of arginine side chains with 1,2-cyclohexanedione under mild conditions eventually led to decreases in translocation-promoting activity, and of heparin binding capacity as measured in a gel-shift assay, but the major portions of these functions were retained even when the four most accessible arginines (attributed to sites in and adjacent to the large loops of the type I modules) were modified. With the modification of additional arginines (attributed to sites in the small loops), both functions were lost. The peptide Gly-Arg-Gly, corresponding to a repeated determinant at the tips of two small loops, inhibited translocation, but arginine alone did not. Cleavage of the large loops by CNBr also led to loss of translocation-promoting activity. The correspondence between the molecular determinants of matrix-driven translocation and those previously found for mesenchymal morphogenesis indicates the utility of this system in the analysis of adhesive interactions of biological importance.

Amino Acid Sequence↗
PubMed1991

Role of transforming growth factor-beta in chondrogenic pattern formation in the embryonic limb: stimulation of mesenchymal condensation and fibronectin gene expression by exogenenous TGF-beta and evidence for endogenous TGF-beta-like activity.

The possible role of TGF-beta-like molecules in skeletal pattern formation in the embryonic vertebrate limb was studied by analyzing the mechanism of enhancement of chondrogenesis in chick wing bud mesenchyme in vitro and testing for the presence and distribution of endogenous TGF-beta-like activity in this tissue. Transient exposure (3-6 hr) to TGF-beta 1 (1-2 ng/ml) on the day after plating resulted in a 1.5- to 2-fold enhancement of accumulation of Alcian blue (pH 1.0)-stainable extracellular matrix 5 days later. The enhancement of differentiation was preceded by an acceleration and an increase in the extent of precartilage condensation formation, visualized by Hoffman Modulation Contrast microscopy a day after TGF-beta treatment. In contrast, neither condensation nor subsequent chondrogenesis was stimulated by transient treatment with TGF-beta 1 on the day of plating. The effectiveness of a TGF-beta treatment regimen in enhancing chondrogenesis was correlated with its effectiveness in stimulating condensation formation. Exposures to the factor for 3-6 hr on the day after plating, which most consistently stimulated both condensation formation and chondrogenesis, also corresponded to a peak in the enhancement of the steady-state level of fibronectin mRNA (fourfold to eightfold over control levels) measured at the end of the treatment period. The elevation in fibronectin mRNA levels brought about by this treatment persisted throughout the period of condensation. Endogenous TGF-beta-like activity was detected in limb mesenchyme: extracts of freshly isolated and cultured limb tissues contained 6-25 pg TGF-beta-like activity per 1 x 10(6) cells by the Mv1Lu cell proliferation inhibition assay, and indirect immunofluorescence using a polyclonal antibody directed against a TGF-beta-related peptide indicated a patchy distribution of endogenous TGF-beta-like reactivity within a day after culture. These findings are discussed in relation to the "fibronectin prepattern" hypothesis for limb pattern formation.

Animals↗
PubMed1991

Ophthalmic features of craniosynostosis.

With the possible exception of aesthetic considerations, the visual system is more involved in craniosynostosis than any other. Changes may be an inherent feature of the pathologic process or occur as a secondary complication. Several of these are potentially devastating, resulting in substantial permanent impairment in visual function. Because these are avoidable if recognized and managed early, prompt involvement of an ophthalmologist in the care of children with craniosynostosis is essential. Improvement in the appearance of these cases cannot obscure the importance of functional problems. In particular, disc edema, optic atrophy, and progressive optic nerve dysfunction may accompany increased intracranial pressure even without evidence of hydrocephalus and even with apparently open fontanelles. Uncorrected refractive error (particularly anisometropia), strabismus, ptosis, and corneal exposure problems are an invitation to the development of amblyopia. If not reversed, this can lead to permanent visual disability. Proptosis and corneal exposure problems are a third potentially treatable cause of functional blindness. Early diagnosis and prompt care will hopefully continue to improve the prognosis for these increasingly treatable children.

Acrocephalosyndactylia↗
PubMed1991

Cryptococcal optic neuropathy in the acquired immune deficiency syndrome.

Cryptococcus neoformans infection occurs frequently in patients with the acquired immune deficiency syndrome (AIDS). Cryptococcal meningitis can result in optic neuropathy. Improvement in afferent visual system dysfunction has not been documented. We report three patients with AIDS who developed either unilateral (1) or bilateral (2) afferent visual system dysfunction. The bilaterally affected patients had visual field deficits compatible with chiasmal involvement. All patients had improvement in their vision following appropriate treatment with amphotericin B. Reactivation of cryptococcal infection was heralded by neuro-ophthalmic manifestations in two patients, in spite of maintenance therapy. Despite the poor overall prognosis, AIDS patients with presumed cryptococcal optic neuropathy can benefit from optimal therapy.

Acquired Immunodeficiency Syndrome↗
PubMed1991

The salting-out behavior of human plasma fibronectin and its possible correlation with heparin-induced cryoprecipitation of the protein.

The solubility of human plasma fibronectin in concentrated ammonium sulfate solutions was measured at pH 7.0 and varying temperatures as well as at 25 degrees C and varying pHs. The salting-out parameters, KS and beta were found to increase linearly with temperature in the range 5 degrees-50 degrees C. KS-pH and beta-pH profiles were found to have maxima at pH 7.0. The dependence of both of the solubility parameters of plasma fibronectin on temperature and pH was thus found to be anomalous. The possibility of a correlation between the heparin-induced cryoprecipitation of fibronectin and the dependence of its solubility parameters on pH and temperature is considered. It is suggested that heparin-induced precipitation of human plasma fibronectin at low temperatures is caused by (i) a cold effect and (ii) conformational change in the protein due to heparin binding.

Ammonium Sulfate↗
PubMed1990

Unfolding transitions of fibronectin and its domains. Stabilization and structural alteration of the N-terminal domain by heparin.

Changes in the conformational state of human plasma fibronectin and several of its fragments were studied by fluorescence emission, intrinsic fluorescence polarization and c.d. spectroscopy under conditions of guanidinium chloride-and temperature-induced unfolding. Fragments were chosen to represent all three types of internal structural homology in the protein. Low concentration (less than 2 M) of guanidinium chloride induced a gradual transition in the intact protein that was not characteristic of any of the isolated domains, suggesting the presence of interdomain interactions within the protein. Intermediate concentrations of guanidinium chloride (2-3 M) and moderately elevated temperatures (55-60 degrees C) induced a highly co-operative structural transition in intact fibronectin that was attributable to the central 110 kDa cell-binding domain. High temperatures (greater than 60 degrees C) produced a gradual unfolding in the intact protein attributable to the 29 kDa N-terminal heparin-binding and 40 kDa collagen-binding domains. Binding of heparin to intact fibronectin and to its N-terminal fragment stabilized the proteins against thermal unfolding. This was reflected in increased delta H for the unfolding transitions of the heparin-bound N-terminal fragment, as well as decreased accessibility to solvent perturbants of internal chromophores in this fragment when bound to heparin. These results help to account for the biological efficacy of the interaction between the fibronectin N-terminal domain and heparin, despite its relatively low affinity.

Circular Dichroism↗
PubMed1990

An assay for heparin by decrease in color yield (DECOY) of a protein-dye-binding reaction.

The interference by heparin and some related molecules with the well-known Bradford dye-binding assay for proteins is used as the basis of a rapid, sensitive method for the quantitation of these polysaccharides. Whereas the available methods for the assay of glycosaminoglycans have lacked specificity for sulfated polyanions in general and for heparin in particular, the procedure described here distinguishes among different uronic acid derivatives and, when performed in conjunction with heparinase digestion or cetylpyridinium chloride precipitation, can be used to determine heparin content of complex biological samples.

Animals↗
PubMed1990

Vascular lesions involving the cranial base: combined surgical and interventional radiologic approach.

Advantages and possible complications of combined surgical and interventional radiologic approach to vascular lesions involving the cranial base are presented in three case examples. The methodology and technology of endovascular embolization and occlusion techniques, selection of embolic materials, functional testing to prevent neurologic injury and surgical implications of these treatment modalities are discussed. Emphasis is placed on individualization of each combined approach relative to the aforementioned factors.

Catheterization↗
PubMed1990

'Generic' physical mechanisms of morphogenesis and pattern formation.

The role of 'generic' physical mechanisms in morphogenesis and pattern formation of tissues is considered. Generic mechanisms are defined as those physical processes that are broadly applicable to living and non-living systems, such as adhesion, surface tension and gravitational effects, viscosity, phase separation, convection and reaction-diffusion coupling. They are contrasted with 'genetic' mechanisms, a term reserved for highly evolved, machine-like, biomolecular processes. Generic mechanisms acting upon living tissues are capable of giving rise to morphogenetic rearrangements of cytoplasmic, tissue and extracellular matrix components, sometimes leading to 'microfingers', and to chemical waves or stripes. We suggest that many morphogenetic and patterning effects are the inevitable outcome of recognized physical properties of tissues, and that generic physical mechanisms that act on these properties are complementary to, and interdependent with genetic mechanisms. We also suggest that major morphological reorganizations in phylogenetic lineages may arise by the action of generic physical mechanisms on developing embryos. Subsequent evolution of genetic mechanisms could stabilize and refine developmental outcomes originally guided by generic effects.

Animals↗
PubMed1990

Anterior ischemic optic neuropathy associated with macrocytic anemia.

A 37-year-old man experienced the acute onset of blurred vision, particularly in the inferior hemifield of his left eye. Neuro-ophthalmic examination showed a left afferent pupillary defect, a left inferior altitudinal visual field deficit, bilateral nerve fiber layer infarcts and hemorrhages, and left optic disc elevation with edema of the nerve fiber bundle. Complete examination and laboratory studies revealed only a severe folate deficiency anemia. This is the first well-documented report of anterior ischemic optic neuropathy associated with anemia in the absence of other systemic abnormalities.

Adult↗
PubMed1989

Non-chemotactic translocation of phagocytic cells mediated by a fibronectin-related human lymphokine.

A fibronectin (FN)-related human lymphokine, macrophage agglutination factor (MAggF), agglutinates monocytes at femtomolar concentrations. Similar concentrations of MAggF translocate monocytes and neutrophils through artificial extracellular matrices by a non-chemotactic adhesive process not dependent on intracellular metabolism (matrix-driven translocation). As is the case with matrix-driven translocation mediated by other FN, MAggF-mediated translocation depends on interaction of the lymphokine amino-terminal heparin-binding domain with cell surface heparin-like molecules. In contrast, lymphokine-mediated agglutination involves interactions between the MAggF cell-binding domain and integrin FN receptors recognizing the Arg-Gly-Asp sequence. MAggF-mediated translocation and agglutination are also dependent on the lymphokine gelatin-binding domain. The extremely high activity of MAggF in translocating and agglutinating monocytes may result from cooperative interactions between multiple lymphokine domains and multiple classes of cell surface receptor molecules. We suggest that MAggF-mediated matrix-driven translocation could act independently of or in addition to chemotaxis in recruiting monocytes and neutrophils to a tissue site of T cell-mediated inflammation. Subsequent interaction of MAggF and monocyte FN receptor could then detain monocytes there.

Cell Aggregation↗
PubMed1989

Wetting, percolation and morphogenesis in a model tissue system.

Artificial tissues constructed of cells or polystyrene beads suspended in a solution of type I collagen will, under appropriate conditions, protrude into regions of similar matrices lacking particles, but containing the extracellular glycoprotein fibronectin. This phenomenon has been termed "matrix-driven translocation". Conditions required for the effect include the presence of heparin-like molecules on the cell or bead surfaces, appropriate concentrations of particles and collagen, and physiological ionic strength and pH. Here we consider the idea that the driving force for the concerted movement of matrix and suspended particles is the thermodynamically spontaneous spreading or wetting behavior of two immiscible fluids bounded by common substrata. Wetting theory is shown to be capable of accounting for the behavior of this model system, but this analysis requires that the two matrix regions constitute separate phases at thermodynamic coexistence. We show that one plausible mechanism for the generation of separate phases is the formation of a percolation network of collagen fibers on a lattice of cells or beads. It is argued that the concepts of wetting and percolation apply to properties in common between the model system and living tissues, and may therefore be used to provide a physical account of aspects of tissue morphogenesis.

Cell Adhesion↗